Enamel and Dentin Bond Strength, Interfacial Ultramorphology and Fluoride Ion Release of Self-etching Adhesives During a pH-cycling Regime

Purpose: This study evaluated the effects of pH cycling on fluoride release and bond strength of two self-etching adhesive systems to both enamel and dentin. The ultramorphology of the interfaces produced by the adhesive systems were also analyzed. Materials and Methods: The buccal surfaces of bovine incisors were flattened to expose enamel and dentin, which were bonded with either Clearfil Protect Bond (CPB) or One-Up Bond F Plus (OBP). The bonded samples were prepared for microtensile bond strength (μTBS) testing, fluoride ion release, and transmission electron microscopy. pH cycling comprised demineralization (8 h/day) and remineralization (16 h/day) cycles for 8 days. The μTBS data were analyzed by two-way ANOVA, while fluoride release was analyzed using the Friedman and Wilcoxon tests. Results: The adhesives presented similar bond strengths to enamel. However, the dentin bond strength of CPB was higher than that of OBP. pH cycling did not influence enamel or dentin μTBS. The amount of fluoride released from the bonded enamel and dentin was low and varied among the groups. The morphological evaluation showed that the thickness of the dentin hybrid layers was similar for both adhesives. Conclusion: The pH-cycling regime did not affect enamel or dentin bond strengths. In enamel, both the self-etching adhesives tested presented similar bond strengths, but in dentin, Clearfil Protect Bond showed higher dentin bonding than One-Up Bond F Plus. Palabras clave: dental enamel, dentin, adhesives, fluoride, bond strength